I currently have a users collection in my Firebase real-time database that contains all my users and a collection that contains the name of books and the ratings(number of thumbs up and down). I am trying to make a application that will display book titles constantly(or the ones that are in my db) so that people can rate them, however I need to be able to check if a user has already viewed this book title or not(this is the part i need help with). Can someone help me with pulling the data from Firebase and comparing it to see if the user has viewed this book title or not. This is what my db setup looks like
Also if someone has a better way of doing this please explain!!!
First, change books_viewed into an array. Read this for arrays in Firebase Realtime Database
Now that it's an array, you can get that as a ArrayList<String> in your app.
public class User {
public ArrayList<String> booksViewed;
... // Other variables
}
Then just use the contains function to check if the book you need to find is in that list
DatabaseReference userRef = FirebaseDatabase.getInstance().getReference().child("Users").child("<UserID>")
userRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user = dataSnapshot.getValue(User.class);
String bookTitleYouAreChecking = "Twilight"
if (user.booksViewed.contains(bookTitleYouAreChecking)) {
// User has viewed
} else {
// User has not viewed
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
// ...
}
})
To solve this, please use the following method that checks if a user had viewed a book or not:
private void checkBookTitle(String bookTitle) {
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = rootRef.child("Users").child(uid).child("books_viewed");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()) {
Map<String, Object> map = (Map<String, Object>) dataSnapshot.getValue();
for (Map.Entry<String, Object> entry : map.entrySet()) {
if (entry.getValue().equals(bookTitle)) {
Log.d(TAG, "User has viewed this book");
} else {
Log.d(TAG, "User has not viewed this book");
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {}
};
ref.addListenerForSingleValueEvent(valueEventListener);
}
Related
I'm trying to get a specific user from the database but I can't, also I would like to check if there is already a node with the same name (uid). I don't want to get the whole list of users and then retrieve one from it because I don't think that's good for perfomance, my idea is to directly get the user from the database
I tried many ways but everything I try returns null, I can't get the values from dataSnapshot. I use an interface to make sure I execute the code after the reading is done
currentUser = FirebaseAuth.getInstance().getCurrentUser();
mUserReference = FirebaseDatabase.getInstance().getReference("users/"+currentUser.getUid());
mUserReference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
user = dataSnapshot.getValue(User.class);
dataStatus.dataIsLoaded(user);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
Here the interface
public interface DataStatus{
void dataIsLoaded(User user);
}
And when I try to get the user it shows NullPointerException
UserUtils userUtils = new UserUtils();
userUtils.getUser(new UserUtils.DataStatus() {
#Override
public void dataIsLoaded(User user) {
mUser = user;
}
});
User creation, when I call this method I do uid = currentUser.getUid()
public void createNewUser(String uid, String name, String email, DataStatus dataStatus) {
mUserReference = mDatabase.child("users").child(uid);
mUserReference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
user = new User(name, email);
mDatabase.child("users").child(uid).setValue(user);
dataStatus.dataIsLoaded(user);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
Here the rules
{
"rules": {
"users": {
"$uid": {
".read": "$uid === auth.uid",
".write": "$uid === auth.uid"
}
}
}
}
Here's how my data base is organized
SOLVED
The problem was a piece of code, which I didn't include here, that was trying to get access to the user outside the dataIsLoaded interface method, and as onDataChange is asynchronous the user hadn't been downloaded yet so it was conflicting with the code.
Welcome to SO community
Please use .child() method instead of cascading nodes with "/" as below
Also check if the value of the datasnapshot is not null using .exists() method
currentUser = FirebaseAuth.getInstance().getCurrentUser();
mUserReference = FirebaseDatabase.getInstance().getReference.child("users").child(currentUser.getUid());
mUserReference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()) {
user = dataSnapshot.getValue(User.class);
dataStatus.dataIsLoaded(user);
}
}
// rest of code
Feel free if you need further support
UPDATE
Please replace your listener with below
currentUser = FirebaseAuth.getInstance().getCurrentUser();
mUserReference = FirebaseDatabase.getInstance().getReference.child("users").child(currentUser.getUid());
Query query = FirebaseDatabase.getInstance().getReference.child("users").orderByKey()
.equalTo(currentUser.getUid());
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot singleSnapshot : dataSnapshot.getChildren()) { // dataSnapshot contains set of returned result of the query
User user = singleSnapshot.getValue(User.class);
if (user != null) {
dataStatus.dataIsLoaded(user);
}
}
}
}
Welcome to SO community.
When did you call your function to read the user content?
it might be an asynchronous problem.
To make sure, make a function where the user is the parameter and call it once you read something from the DB (onDataChange).
Plus, did you try to print out what is inside " user " when you read it? if it gives you null, the problem is within the path for sure. If so, use .child("users").child(currentUser.getUid())
I'm trying to set up an order placing system.
Once the user is verified via email, it can create/update/delete order.
Order is saved into Firebase Real-time Database and users are saved in Authentication.
I would like to allow user to only see/edit orders that were placed by this specific user. Basically make use of UserUID from Authentication section.
public class FirebaseDatabaseHelper {
private FirebaseDatabase mDatabase;
private DatabaseReference mReferenceOrders;
private List<Order> orders = new ArrayList<>();
public interface DataStatus{
void DataIsLoaded(List<Order> orders, List<String> keys);
void DataIsInserted();
void DataIsUpdated();
void DataIsDeleted();
}
//Initialize Database object
public FirebaseDatabaseHelper() {
mDatabase = FirebaseDatabase.getInstance();
mReferenceOrders = ((FirebaseDatabase) mDatabase).getReference("order");
}
public void readOrders(final DataStatus dataStatus){
mReferenceOrders.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
orders.clear();
List<String> keys = new ArrayList<>();
for(DataSnapshot keyNode : dataSnapshot.getChildren()) {
keys.add(keyNode.getKey());
Order order = keyNode.getValue(Order.class);
orders.add(order);
}
dataStatus.DataIsLoaded(orders,keys);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
public void addOrder(Order order, final DataStatus dataStatus) {
String key = mReferenceOrders.push().getKey();
mReferenceOrders.child(key).setValue(order).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
dataStatus.DataIsInserted();
}
});
}
// Update and Delete methods
public void updateOrder(String key, Order order, final DataStatus dataStatus){
mReferenceOrders.child(key).setValue(order).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
dataStatus.DataIsUpdated();
}
});
}
public void deleteOrder(String key, final DataStatus dataStatus){
mReferenceOrders.child(key).setValue(null).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
dataStatus.DataIsDeleted();
}
});
}
}
Here's what I was thinking:
When a user creates a new order then a UserUID is added to a database and nested inside 'order' so now each order can be assigned to a user that created it.
Now the next step would be to display this order to a user that created it but only if cust_id (in order) matches UserUID of a logged in user. Would that be a good approach?
Yes, it is a good approach, now you need to add to your Firebase Realtime Database now branch with your users data based on userUID, like this:
Thanks to this you will be able to connect your users with their orders data and besides you can save here more specific user data like "how many orders user create", "how many orders are active" etc.
I have added a user_id to an 'order' in the Firebase database so each order can be assigned to its user.
I got the parameter for user_id by fetching a UserUID from an Authentication section of Firebase when a new user is logged/signed in.
Screenshot of UserUID in Authentication section of Firebase
I got this value in my code by adding the following:
private FirebaseAuth mAuth;
order.setUser_id(mAuth.getCurrentUser().getUid());
Once I got the user_id assigned to each order I've created a following if statement which is implemented in my readOrders function which you can see in my original post above:
public void readOrders(final DataStatus dataStatus){
mReferenceOrders.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
orders.clear();
List<String> keys = new ArrayList<>();
for(DataSnapshot keyNode : dataSnapshot.getChildren()) {
keys.add(keyNode.getKey());
Order order = keyNode.getValue(Order.class);
**if (order.getUser_id().equals(mAuth.getUid())) {
Log.d("FirebaseDatabaseHelper", "match");
orders.add(order);
}else {
Log.d("FirebaseDatabaseHelper", "error");
}**
}
dataStatus.DataIsLoaded(orders,keys);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
So basically now when the new user logs in, there will be nothing to show because the user_id won't match with any of the user_id's inside Order database.
I'm not sure how efficient this method will be when more users/orders will be added so I'll have to do some testing.
Please advise if this is the best approach!
I need to display list of all users (Name, date and status) in a single list where status="Leave Pending" as pointed by red arrow. I wrote the following code to do this but it is not giving me username in the list.
As I used nested for each loop for this but not getting username. Kindly suggest me some solution to display the username too.
In my code:
LeaveRequestsInfo is the model class for mapping data.
requestsInfo is the object of modal class in which i am mapping my data.
listViewRequests is the ListView
requestsList is the object of List
To solve this, you need to query the database twice, once to get the user id and second, based on that id to get the name of the user. This can be done in a very simple way, using the String class, so please use the following lines of code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference attendanceRef = rootRef.child("Attendance");
Query query = attendanceRef.orderByChild("status").equalsTo("Leave Pending");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String id = ds.child("id").getValue(String.class);
DatabaseReference idRef = rootRef.child("Users").child(id);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String name = dataSnapshot.child("name").getValue(String.class);
Log.d("TAG", name);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
idRef.addListenerForSingleValueEvent(eventListener);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
query.addListenerForSingleValueEvent(valueEventListener);
The result in your logcat will be all the names of all attendances where the status is Leave Pending.
I am working on app where I want to show the data only of the users whose contact numbers are saved in the phone. So, I retrieved a list of contact numbers contactList. Now, I want to get all the contactList user's post from Firebase. Is there any way I can ask the Firebase for only those nodes in my contactList. One Way is to retrieve all users and then get relevant users from that (like I did below). Is there any better way to do so ?
Users: {
7828272892 : {
name: xyz,
gender: male,
phoneNo: 7828272892
Posts: {
SomeKey1: {
content: "This is post 1", Var2: "kkk"} }},
7924272894 : {name: abc, gender: male, phoneNo: 7924272894}
}
Code:
databaseReference.child("Users").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
List<Post> allItems = new ArrayList<Post>();
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
if (contactList.contains(postSnapshot.child("phoneNo").getValue())) {
// retrieve posts
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Is there any way I can ask the firebase for only those nodes in my contactList?
Yes, the way in which you already do this.
Is there any better way to do so?
The way in which you do this is a common practice used in Firebase. You query the database and check is the data already exists in the list, in your case in the contactList. If the list contains that phoneNo then you can retrieve the posts.
Try this code to read multiple nodes data..
mFirebaseInstance = FirebaseDatabase.getInstance();
mDatabase = mFirebaseInstance.getReference("usersDb/UserTable");
mDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
mUserList.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
User user = dataSnapshot1.getValue(User.class);
mUserList.add(user); // add all data into list.
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
In my application I want to retrieve a single value from a particular id. The below screenshot is my database structure:
I want to retrieve the count of likes from database.
This is what I have tried:
public String getLikesCount(String USER_ID){
mref = FirebaseDatabase.getInstance().getReference("user").child(USER_ID);
return currentLike;
}
I don't know what to do after this to get likes count. Can anyone help me please?
do the following:
mref = FirebaseDatabase.getInstance().getReference("user").child(USER_ID).child("likes");
mref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String likes = dataSnapshot.getValue(String.class);
//do what you want with the likes
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});